Tetrahydrobiopterin

2022-04-07: reference:

Tetrahydrobiopterin #

• Antioxidant, as it opposes dihydrobiopterin which uncouples NOS. It’s a matter of redox.

• It binds competitively with AAAH’s feedback-inhibiting products, i.e. dopamine. and also negatively regulates GFRP (GTPCH regulatory protein 1)

• Ultimately synthesized via GTP, the rate-limiting enzyme being GTP cyclohydrase (GTPCH), which is colocalized with Tyrosine Hydroxylase (so other AAAHs I’m sure?)

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  • After being used as a cofactor by eNOS/AAAH, it actually becomes BH4-4α-Carbinolamine, then PCD (pterin carbinolamine dehydrase)->qBH2, which tautomerizes into with BH2.
  • PTPS: pyruvoyl tetrahydrobiopterin synthase, and SR: Sepiapterin reductase.

• After synthesis, it is recycled via methylation with Folate.

  • Pteridine: now you see how; folate has this.

• Tetrahydrobiopterin causes mitochondrial dysfunction in dopaminergic cells: Implications for Parkinson’s disease

  • Lower levels (along with Folate in Schizophrenia)